MOTHERS who exercise during pregnancy are helping to boost their child’s IQ, according to research by American psychologists.

In a challenge to the conventional wisdom that intelligence is 80% genetic, Richard E Nisbett, a psychologist and father of two, argues that recent findings point to a pivotal role for mothers. Fathers, whether absent or doting, have relatively little influence over their offspring’s intelligence.

In a new book, Intelligence and How To Get It, Nisbett highlights the important part the mother plays in shaping her children’s ability to learn and reason, starting shortly after conception.

“Children whose mother exercised 30 minutes a day score around eight points higher on standard IQ tests than children whose mothers were more sedentary,” he said last week. “Breast-feeding for up to nine months may increase IQ by as much as six points.”

Previous generations of mothers were encouraged to avoid doing much exercise after the first three months of pregnancy. The latest research suggests that using light weights, stretching and even running can be beneficial to some, though not all.

Official advice in Britain is that the more active and fit most women are during pregnancy, the more easily they will adapt to their changing shape and weight gain. It will also help them to cope with labour.

In Hollywood, both Halle Berry, the actress, and Chris-tina Aguilera, the singer, have talked about doing “baby-friendly” track exercise during their pregnancies.

Isla Fisher, the Australian actress, said she would never undertake exercise for herself, as she hated it, but tried it for her infant, Olive.

“Exercising large muscle groups increases the growth of neurons and adds to the blood supply of the brain,” writes Nisbett. Exercise and breast-feeding combined, he says, will raise a typical child’s IQ to about 114, 14 points above average.

Nisbett also argues that the way mothers talk to their children can help to increase their IQ. He encourages parents to ask questions to which they already know the answers and, if necessary, explain how they know them. This is said to encourage children to seek answers to their own questions.

Nisbett praises middle-class families in particular for setting what he calls “anticipation exercises”, in which children are asked to make predictions, such as where a submerged duck will surface in a pond.

He also says that children who successfully complete a task should be praised for their hard work rather than be called clever, because hard work is something over which they have control.

His ideas are catching on. In Texas, mothers are being taught how to create an “educationally rich” atmosphere at home for their children, especially during the summer holidays.

Nisbett says the choice of school also helps. He praises Kipp, or Knowledge Is Power, the fast-expanding p r i v a t e school chain in the US, which trains poor urban children and their mothers to study 12 hours a day and take only short holidays. Kipp IQ scores match those of expensive private schools.

He admitted there is a thin line between mothers who artfully guide their children towards success and “helicopter parents” who hover over their offspring and suck all the pleasure out of their childhood. “But the mother is the most important IQ agent here. In families dominated by a father, there are higher mathematical skills but that’s all we contribute, I’m afraid,” he said.

The responsibility is not welcomed by all mothers. Ayelet Waldman, a Californian author who caused a stir in 2005 when she admitted that she loved her husband more than her three children, said mothers were already under too much pressure.

Waldman, 44, whose latest book, Bad Mother: A Chronicle of Maternal Crimes, Minor Calamities and Occasional Moments of Grace, is published this week, said mothers were under pressure to take part in their children’s education in a way their own parents never contemplated.

“Just remember . . . little you do to your kids damages them for ever,” she said.

“Lighten up.”

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